iNES Mapper 176 denotes the 8025 enhanced MMC3 chipset. It used by many multicarts, Chinese single-game and educational computer cartridges, and Techno Source's Intellivision X2 Plug-and-Play console. Incompatible variations exist are denoted via NES 2.0 Submapper.
Submappers | ||||||||||||
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# | PCB codes | UNIF MAPR | MMC3 | Outer bank registers | Example | |||||||
Ext. mode | PRG bits | $46/47 | 1SM | Extra WRAM | Address mask | PRG A21+ | CHR A21+ | CNROM latch | ||||
0 | LP-8002KB, SFC-12B | BMC-Super24in1SC03 | - | 6 | normal | - | - | $Fxx3 | - | - | - | YH-xxx multicarts, Rockman 6-in-1 |
1 | FK-xxx/BS-xxx | BMC-FK23C/BMC-FK23CA | $5FF3.1 | 8 | normal | - | - | $Fxx3 | - | - | yes | FK-xxxx multicarts |
2 | FS005/FS006 | WAIXING-FS005 | $5FF3.1 | 6 | swapped | yes | $A001.0-1 | $Fxx3 | $5xx0.3/7, $5xx2.6-7/5 | - | - | Waixing 2005+ re-releases, 245-in-1 Real Game |
3 | JX9003B | - | - | 8 | normal | - | - | $Fxx7 | $5xx5 | $5xx6 | - | Super Mario 160-in-1 Funny Time |
4 | ? | - | - | 6 | normal | - | - | $Fxx3 | $5xx2.7 | - | - | GameStar Smart Genius Deluxe |
FS005 (Submapper 2) can disable the registers in the $5000-$5FFF range using the RAM Configuration Register ($A001). The same register also enables a mixed CHR-ROM/CHR-RAM mode that is similar to INES Mapper 195.
Mask: $5xx7 (Submapper 3), $5xx3 (all others), x determined by solder pad setting
7654 3210 ---- ---- PCTm PMMM |||| |||| |||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode) |||| | 0: MMC3 PRG Mode, 2 MiB/512 KiB Outer PRG Bank Size |||| | 1: MMC3 PRG Mode, 256 KiB Outer PRG Bank Size |||| | 2: MMC3 PRG Mode, 128 KiB Outer PRG Bank Size |||| | 3: NROM-128 PRG Mode, 16 KiB PRG at $8000-$BFFF mirrored at $C000-$FFFF |||| | 4: NROM-256 PRG Mode, 32 KiB PRG at $8000-$FFFF |||| | 5: UNROM PRG Mode, 16 KiB PRG at $8000-$BFFF, inner bank #7 at $C000-$FFFF |||| | 6-7: Never used |||| +---- PRG A21 (Submapper 2 only) |||+------ Select Outer CHR Bank Size ||| 0: In MMC3 CHR Mode: 256 KiB ||| In CNROM CHR Mode: 32 KiB (Submapper 1 only) ||| 1: In MMC3 CHR Mode: 128 KiB ||| In CNROM CHR Mode: 16 KiB (Submapper 1 only) ||+------- Submappers 0/1 with both CHR-ROM and CHR-RAM (e.g. SFC-12B PCB): || 0: Select CHR-ROM || 1: Select CHR-RAM || Submapper 1 with $5xx0.6=1: || 0: Enable CNROM latch (CNROM mode) || 1: Disable CNROM latch (NROM mode) |+-------- CHR A10-12 Mode | 0: from MMC3 | 1: from PPU +--------- PRG A22 (Submapper 2 only) Power-on value: $00
Mask: $5xx7 (Submapper 3), $5xx3 (all others), x determined by solder pad setting
7654 3210 ---- ---- .PPP PPPP ||| |||| +++-++++- PRG A20..A14 Power-on value: $00
Depending on the PRG banking mode set via $5xx0, only the higher bits of this register are applied:
PRG A.. 21111111 09876543 -------- MMMMMMMM Submappers 1/3 in PRG Mode 0 (MMC3 2 MiB) or Extended MMC3 Mode BBMMMMMM Submappers 0/2/4 in PRG Mode 0 (MMC3 512 KiB) BBBMMMMM PRG Mode 1 (MMC3 256 KiB) BBBBMMMM PRG Mode 2 (MMC3 128 KiB) BBBBBBBC PRG Mode 3 (NROM-128) BBBBBBCC PRG Mode 4 (NROM-256) BBBBLLLC PRG Mode 5 (UNROM) M: Bit comes from MMC3 ($8000.6/7 or fixed bank) B: Bit comes from PRG Base Register ($5xx1) L: Bit comes from UNROM Latch ($8000-$FFFF or fixed bank) C: Bit comes from CPU
Mask: $5xx7 (Submapper 3), x determined by solder pad setting
7654 3210 ---- ---- .... PPPP |||| ++++- PRG Base A24..A21 Power-on value: $00
Mask: $5xx7 (Submapper 3), $5xx3 (all others), x determined by solder pad setting
7654 3210 ---- ---- ccdC CCCC |||| |||| ++++-++++- CHR A20..A13 ||+------- PRG A25 (Submapper 2 only) ++-------- PRG A24..A23 (Submapper 2 only) +--------- PRG A21 (Submapper 4) Power-on value: $00
Depending on the CHR banking mode set via $5xx0, only the higher bits of this register are applied:
CHR A.. 21111111111 09876543210 ----------- BBBMMMMMMMM MMC3 CHR Mode ($5xx0.6=0), 256 KiB ($5xx0.4=0) BBBBMMMMMMM MMC3 CHR Mode ($5xx0.6=0), 128 KiB ($5xx0.4=1) BBBBBBLLPPP CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 32 KiB ($5xx0.4=0), Submapper 1 only BBBBBBBLPPP CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 16 KiB ($5xx0.4=1), Submapper 1 only BBBBBBBBPPP NROM CHR Mode ($5xx0.6=1, $5xx0.5=1 or Submapper other than 1) M: Bit comes from MMC3 ($8000.0-5) B: Bit comes from CHR Base Register ($5xx2) L: Bit comes from CNROM Latch ($8000-$FFFF) P: Bit comes from PPU
Mask: $5xx7 (Submapper 3), x determined by solder pad setting
7654 3210 ---- ---- .... PPPP |||| ++++- CHR Base A24..A21 Power-on value: $00
Mask: $5xx3, x determined by solder pad setting
7654 3210 ---- ---- .?.. .?E. | +- Extended MMC3 Mode 0: disable 1: enable Power-on value: $00
Most multicarts write value $44 rather than $00 to disable Extended MMC3 Mode. Hardware tests do not indicate any difference in behavior between writing $00 and $44.
Mask: $E003 7654 3210 ---- ---- .... ..MM ++- Select nametable mirroring 0: Vertical 1: Horizontal 2: Single-screen, page 0 (Submapper 2 only) 3: Single-screen, page 1 (Submapper 2 only) Power-on value: $00
Single-screen mirroring is only available when the RAM Configuration Register is enabled ($A001.5).
Mask: $E003
This register functions like MMC3 register $A001 until bit 5 is set, which turns it into the RAM Configuration Register.
7654 3210 ---- ---- RFE. SCWW ||| |||| ||| ||++- Select 8 KiB PRG-RAM bank at $6000-$7FFF. Ignored if Bit 5 is clear. ||| |+--- Select the memory type in the first 8 KiB of CHR space. Ignored if Bit 5 is clear. ||| | 0: First 8 KiB are CHR-ROM ||| | 1: First 8 KiB are CHR-RAM ||| +---- Unknown ||+------- RAM Configuration Register Enable || 0: RAM Configuration Register disabled, $A001 functions as on MMC3, 8 KiB of WRAM || 1: RAM Configuration Register enabled, 32 KiB of WRAM |+-------- Outer Bank Registers Enable. Ignored if Bit 5 is clear. | 0: Outer Bank Registers disabled, $5000-$5FFF maps to the second 4 KiB of the 8 KiB WRAM bank 2 | 1: Outer Bank Registers enabled in the $5000-$5FFF range +--------- PRG RAM enable (0: disable, 1: enable) Power-on value: $00
In UNROM Mode (PRG Mode 5), writing to this address range changes the 16 KiB inner PRG bank at $8000-$BFFF.
In CNROM Mode, writing to this address range changes the inner CHR bank.
Mask: $E003 (verified on real hardware)
Some multicart games depend on writes to $9FFF not doing anything as a result of the MMC3 address mask being $E003 rather than the standard $E001.
If the "Extended MMC3 Mode" bit in register $5xx3 is clear, then these registers function identically to the MMC3. On Submappers 1 and 2, if the "Extended MMC3 Mode" bit is set, four more bank registers become available at $8000/$8001, so that the original two 2 KiB CHR banks become four 1 KiB CHR banks, and the two fixed 8 KiB PRG banks become selectable, similar to the RAMBO-1. Register $8000 if $5xx3 bit 1 is set:
7 bit 0 ---- ---- CP.. RRRR || |||| || ++++- Specify which bank register to update on next write to Bank Data register || $0: Select 1 KB CHR bank at PPU $0000-$03FF (or $1000-$13FF) || $1: Select 1 KB CHR bank at PPU $0800-$0BFF (or $1800-$1BFF) || $2: Select 1 KB CHR bank at PPU $1000-$13FF (or $0000-$03FF) || $3: Select 1 KB CHR bank at PPU $1400-$17FF (or $0400-$07FF) || $4: Select 1 KB CHR bank at PPU $1800-$1BFF (or $0800-$0BFF) || $5: Select 1 KB CHR bank at PPU $1C00-$1FFF (or $0C00-$0FFF) || $6: Select 8 KB PRG ROM bank at $8000-$9FFF (or $C000-$DFFF) || $7: Select 8 KB PRG ROM bank at $A000-$BFFF || $8: Select 8 KB PRG ROM bank at $C000-$DFFF (or $8000-$9FFF) || $9: Select 8 KB PRG ROM bank at $E000-$FFFF || $A: Select 1 KB CHR bank at PPU $0400-$07FF (or $1400-$17FF) || $B: Select 1 KB CHR bank at PPU $0C00-$0FFF (or $1C00-$1FFF) |+-------- Invert PRG A14 +--------- Invert CHR A12 Power-on values: * Standard MMC3 Registers $0-$7: $00, $02, $04, $05, $06, $07, $00, $01 * Extended MMC3 Registers $8-$B: $FE, $FF, $FF, $FF
The address mask in the $5000-$5FFF range is determined by the solder pad setting:
Pad setting Address mask ----------- ------------ 0 $5013 1 $5023 2 $5043 3 $5083 4 $5103 5 $5203 6 $5403 7 $5803
Later Waixing games (and re-releases of earlier games) use the RAM Configuration Register for copy-protection purposes:
Hacked ROMs can be detected by them writing to $5000/$5010/$5013 but then no longer jumping to $0100.
Categories: MMC3-like mappers, Mappers with scanline IRQs, Mappers with large PRG RAM, NES 2.0 mappers with submappers, Multicart mappers, MMC3 with CHR ROM and CHR RAM, INES Mappers